The invention relates to a fuel cell. A fuel cell includes a cathode, an electrolyte and an anode. The cathode is supplied with a fuel such as hydrogen.
There are various types of fuel cells, for example, SOFC fuel cells or PEM fuel cells.
A SOFC fuel cell is also called high temperature fuel cell, since its operating temperature is about 900.degree. C. At the cathode of a high temperature fuel cell, oxygen ions are formed in the presence of an oxidizing agent. The oxygen ions pass through the electrolyte and recombine at the anode side with the hydrogen from the fuel to form water. During recombination, electrons are released, whereby electric energy is generated.
The operating temperature of a PEM fuel cell is about 80.degree. C. In the presence of fuel hydrogen ions are formed at the anode of a PEM fuel cell by means of a catalyst. The hydrogen ions pass through the electrolyte and are combined with the oxygen from the oxidizing agent to form water. In the process, electrons are released whereby electric energy is generated. Hydrogen can be produced by reforming from methanol or methane.
For the generation of a large power output, several fuel cells are generally serially connected to form a so-called fuel cell stack. The element interconnecting two fuel cells is known as an interconnector.
In order to introduce the oxidizing agent and the fuel into a fuel cell or, respectively, into a fuel cell stack, pumps compressors or other pumping means are required. Depending on the type of the fuel cell unconsumed oxidizing agent and unconsumed fuel are subsequently conducted out of the fuel cell.
If pumps or similar means are used for moving the fuel and oxidizing agents through the fuel cell, the efficiency of the fuel cell is detrimentally affected since pumps consume usable (electric) energy. With pumps, furthermore, the number of moving components is increased which a fuel cell or fuel cell stack includes. A large number of moving parts is disadvantageous since the reliability of such an apparatus decreases and its costs increase with an increasing number of moving parts.
JB 59-8278(A) (Patent Abstracts of Japan, E-240 of Apr. 21, 1984, Vol. 8, No. 88) discloses an arrangement for transporting the required media through the fuel cell by convection with the aid of heating elements. However, such heating elements also consume energy and consequently, they detrimentally affect the efficiency of the whole apparatus.
It is the object of the present invention to provide a fuel cell which has a greater efficiency than the fuel cells known in the art and which furthermore is more reliable.